Dynamic HTML in Action
The general idea of multimedia is to give the user a more exciting experience than is offered by static text and graphics on a page. Some examples of multimedia include:
- An animated logo
- A news site offering video clips of broadcast news stories instead of simply text
- A movie company posting movie previews to the Web
- An online music store offering sample audio clips from its CD selection
- An individual adding some favorite background audio to a personal Web page
- A company training its employees through interactive online courses
Designing Web pages that use multimedia to do all these things while remaining efficient is a challenging task. One constant issue encountered when using multimedia is the lack of available bandwidth needed to transfer the sizable amount of information that makes up most multimedia files. Let's take a look at some of the major types of multimedia.
Audio and Video
Audio and video were the first types of multimedia to be made available over the Web. Both can be played either directly in the browser or outside the browser in their own windows. There are also a number of different options for distributing these large files. Some of these involve downloading the entire file before it is played, while others play the file while it is downloading, a technique known as streaming. This chapter covers some basic cross browser ways of adding sound and video to a page. Chapter 18 really delves into the subject with a discussion of some of the more powerful multimedia controls.
Multimedia Controls
A new approach to the bandwidth problem was introduced in Microsoft Internet Explorer 4 with the DirectAnimation Multimedia Controls. These controls (which are supported only in Internet Explorer) are designed to eliminate media files by simply transferring instructions to the browser that tell it how to create and display an object. In some cases, this provides a solution to the bandwidth problem. For example, a file containing a video of a rotating graphic would be many times the size of a file containing instructions that produce the same video effect using the DirectAnimation Multimedia Controls. Four DirectAnimation Controls ship with Internet Explorer:
- The Structured Graphics control is used to create lightweight vector graphics that can be scaled or rotated in three dimensions.
- The Sequencer control manages the timing and sequencing of events on the page.
- The Path control positions the elements and directs where they move on the page over a set period of time.
- The Sprite control allows for the addition of still or animated images to a page and offers control over the frame rate and playback.
See Chapter 19 for more information on these controls.
Other Types of Multimedia
Web browsers can also display a variety of other types of media files, including MacroMedia Flash and ShockWave, Virtual Reality Markup Language (VRML), and Math Markup Language (MathML). Because these formats are not core technology in browsers and creating them frequently requires third-party editing products that must be purchased, we will not delve into them in this text.
Macromedia Flash is one of the most commonly used types of alternative multimedia. It allows for the creation of everything from buttons with built-in sound effects to a complete multimedia presentation with audio, video, and line graphics. It has great support for vector (line-based) graphics and produces very small files. Playback of flash files is done with Flash player (free and available for all common browsers and included with Internet Explorer versions 4 and later). Creating these files requires an editing program that can be purchased from Macromedia. Learn more about Flash at www.macromedia.com.
ChromeEffects is a new set of features that enables high-quality multimedia to be sent over the Internet to users of Internet Explorer 5 or later who are using Microsoft Windows 98 or Microsoft Windows 2000 on modern machines. An example of a fairly simple ChromeEffects project would be a spinning cube that has different video streams and HTML pages playing on each face. Because ChromeEffects appeals to a more limited audience, it won't be covered in this book.